Even if you don't care about JB but you're an upgrader or a reseller, being on a patched version of iOS will definitely impact value and at the very least, desirability.
Something else to consider for stock advocates 😉
It's dissapointing that JB encourages hardware sales, but once Apple has made the numbers, they don't mind reversing the original reason you bought the devices to begin with, even though it "voids the warranty" and isn't supported by them. This has how it's always been, but if I was Mr. Cook, and knew people were gonna jailbreak regardless of how much the company discourages it (with a snooty KB article and Genius Bar unlock placards back in the day), I'd offer a dev friendly IPSW where you have root access cooked in. With a dev account, you have more flexibility anyways. Might as well go the full mile. It only encourages innovation since they "borrow" from JB devs with every iOS iteration.